2021 Mercedes-Benz CLA Reliability Report

Sudden loss of drive is the main complaint. Cars go into limp mode, stop accelerating, or shut off completely at highway speed, sometimes showing warnings such as "car cannot shift" or a battery failure message. Dealers have blamed the transmission control unit, the 48-volt system and failed cylinder heads. Owners report outright transmission failures at 15,000 and 22,000 miles. A few describe the car rolling while in Park. Several stalls left drivers stranded in traffic or nearly rear-ended.

Phantom braking with adaptive cruise control is the main pattern. The car misreads speed signs, including exit ramp and minimum speed signs, and brakes hard from highway speed, in some cases down to 15 or 20 mph. Dealers often cannot reproduce it, and software updates have not cured it for some owners. Switching off automatic speed control stops the problem for some drivers, but one saw no change after turning off the sign settings. Other reports, including one from a CLA 250 owner, describe sudden power loss. One crash with injury is listed.

Brake faults run in both directions. Some cars brake hard on their own in light traffic with no obstacle ahead. Others fail to stop when the driver presses the pedal at parking speeds, and two of these reports involve crashes, with four injuries listed in total. In one case the electric parking brake seized while parking and left the car unable to move until a caliper repair. Owners also report grinding noises and a car that nudges forward while in Park. Warning lights rarely come on beforehand.

The main complaints are fast tread wear and damaged tires. Original tires wore to zero tread or near bald between 22,000 and 26,500 miles. Owners also report sidewall bubbles after potholes, tread separation that causes vibration and a flapping noise, and repeated flats on large 21-inch wheels. Some cars came without a spare. Continental ProContact GX SSR tires on the GLA and GLB show up more than once. One crash with injury is listed at 11,000 miles, but the report does not link it to a specific tire defect.

Front ball joint separation is the most serious pattern. In two reports the right front ball joint broke at low speed and the wheel came away from its mounting. One car slid into a parked vehicle. In the other, the driver saw a transmission fault warning and heard grinding first. The remaining filings are vague: debris hitting the underside and setting off the airbags, skidding on summer tires in snow, and a list of mixed faults on a new car. Most of the crash, fire and injury flags come from one unreadable report.

This small group covers airbag warnings and injuries from deployment. One driver was cut and burned when the airbags deployed in a 30 to 35 mph collision. Another owner sees a passenger airbag malfunction warning alongside blind spot and brake assist faults that the dealer has tried to fix 5 times. A third reports a burning smell, an abnormal noise and a passenger airbag warning light. With only 3 complaints, the reports share no common cause.

Belts that fail to lock are the common thread. One owner reports a driver retractor that does not lock. In another case the driver's belt did not hold during a high-speed rear-end crash, and the driver suffered a head injury. A dealer has not reproduced that failure. In a GLS, a third-row buckle latch failed under hard braking and children fell from their seats, and the dealer replaced the latch. With only 3 complaints, the sample is small.